Corrosion inhibitor containing sulfurized tall oil

ABSTRACT

A CORROSION INHIBITOR INCLUDES AN AMINE SALT OF SULFURIZED TALL OIL FATTY ACIDS, OR EQUIVALENTS. THE USUAL EMULSION PROBLEMS ACCOMPANYING USE OF AMINE SALTS OF ORDINARY TALL OIL FATTY ACIDS ARE OVER COME BY SULFURIZING THESE ACIDS, USING AN EXCESS OF THE SULFURIZED ACIDS OVER THE AMOUNT NECESSARY TO NEUTRALIZE THE AMINE AND INCLUDING AS AN EXTENDER OR COSURFACTANT AN ETHOXYLATED POLYPROPYLENE GLYCOL. THE INHIBITOR SHOULD ALSO INCLUDE A LITTLE WATER, TO REDUCE HAZING, AND A LOW MOLECULAR-WEIGHT ALCOHOL, TO REDUCE THE POUR POINT OF THE COMPOSITION, AND A SOLVENT TO DECREASE THE AMINE SALT CONCENTRATION.

United States Patent Ofifice 3,703,477 Patented Nov. 21, 1972 3,703,477 CORROSION INHIBITOR CONTAINING SULFURIZED TALL OIL Loyd W. Jones, Tulsa, Okla, assignor to Pan American Petroleum Corporation, Tulsa, Okla. No Drawing. Filed Jan. 18, 1971, Ser. No. 107,585

Int. Cl. 023i 11/16, 11/14 US. Cl. 252-391 8 Claims ABSTRACT OF THE DISCLOSURE A corrosion inhibitor includes an amine salt of sulfurized tall oil fatty acids, or equivalents. The usual emulsion problems accompanying use of amine salts of ordinary tall oil fatty acids are overcome by sulfurizing these acids, using an excess of the sulfurized acids over the amount necessary to neutralize the amine and including as an extender or cosurfactant an ethoxylated polypropylene glycol. The inhibitor should also include a little water, to reduce hazing, and a low molecular-weight alcohol, to reduce the pour point of the composition, and a solvent to decrease the amine salt concentration.

For many years amine salts of fatty acids have been used to inhibit corrosion in oil fields and refineries. These salts have inhibited corrosion by hydrogen sulfide, oxygen, carbon dioxide, low molecular-weight carboxylic acids, and combinations of these corrosive materials. Several acids and several amines have been used to form the salts. Examples are found in US. Pats. 2,598,213 Blair; 2,736,658 Pfohl et al.; 2,756,211 Jones; 2,914,475 Oxford, and the like. The mixed fatty acids from tall oil have a low cost but very good quality control. In spite of their low cost and good quality, these acids have not been widely used to form amine salt corrosion inhibitors. The reason is that these amine salts tend to stabilize emulsions between oil and water.

Some efforts have been made to overcome these emulsion problems. For example, my Canadian Pat. 713,993 describes the use of various combinations of surface-active agents to overcome this emulsifying tendency.

An object of this invention is to provide a corrosioninhibiting composition based on tall oil fatty acids, or their equivalents, which overcomes the emulsion-stabilizing problem without relying on complex combinations of surface-active agents. Other objects will be apparent from the following description and claims.

SUMMARY OF THE INVENTION In general, I accomplish the objects of my invention by sulfurizing the tall oil fatty acids. Usually, however, this does not provide a complete solution to the problem. For better results, an excess of the sulfurized acids over the amount necessary to neutralize the amine should be used. An ethoxylated polypropylene glycol must also be included, not only for emulsion control, but also to act as a cosurfactant and improve the corrosion-inhibiting ability of the amine salt.

The composition can probably be best described by presenting a preferred formulation and then considering variations. The preferred composition is presented in Table I, together with permissible ranges of concentrations.

TABLE I Concentration,

percent by wt.

Preferred Range Material:

Amine salt; 30 8-50 Extender (eosurlactant) 5 2-10 Water 2 0-4 Pour point depressant 10 0-90 Solvent 53 40-90 The acid portion of the amine salt is sulfurized, unsaturated fatty acids. The fatty acids before the addition of sulfur are preferably tall oil acids from which at least most of the rosin acids have been removed to leave the fatty acids. Such acids are commercially available containing about percent unsaturated fatty acids, mostly oleic and linoleic, together with around 5 percent saturated fatty acids and about 10 percent of other materials, such as rosin acids and unsaponifiables. While these tall oil fatty acids are preferred because of their low cost and constant quality, very similar mixed unsaturated fatty acids containing from 16 to 22 carbon atoms per molecule are available from other sources, such as corn oil, cotton seed oil, peanut oil, and the like. Acids from such sources are equivalents of tall oil fatty acids for my purposes.

The acids are sulfurized by simply adding sulfur and heating to about 350 to 370 F. for about 30 minutes. The sulfur dissolves at a lower temperature but rapid reaction takes place only at temperatures above about 320 F. The temperature should not exceed 370 F. for very long since decomposition begins to take place at about this temperature.

The amount of sulfur used may be between about 1 and 4 moles of sulfur per mole of acids. For example, one sample of tall oil fatty acids had a mole-combining weight of about 305 as determined by titration. This sample was reacted with sutficient sulfur to provide about 19 percent sulfur by weight in the sulfurized acid. The result was a very satisfactory sulfurized acid.containing about 2 moles of sulfur per mole of the mixed acids from tall oil. Four moles of sulfur per mole of acid produces minor solubility problems. Larger amounts of sulfur cause greater problems. Therefore, not more than 4 moles of sulfur per mole of acid should be used. Not less than about 1 mole of sulfur per mole of acids should be used, if substantial effects of the sulfur are to be obtained. Preferably from about 2 to about 3 moles of sulfur per mole of acids should be used.

Tests indicate that either the straight-chain amines, such as those described in US. Pat. 2,756,211 Jones, or substituted heterocyclic amines, such as the substituted imidazolines, described in US. Pat. 2,468,163 Blair et al., may be used to form salts with the sulfurized acids. The best amines from the standpoint of avoiding emulsion formation seem to be the diamines described in U.S. Pat. 2,736,658 Pfohl et al. In general, these amines can be described as the aliphatic amines and substituted imidazolines having an aliphatic hydrocarbon radical containing from about 8 to about 22 carbon atoms. Preferably, the amine has the formula RNH(CH NH in which R is a mixture of aliphatic hydrocarbon radicals containing from about 16 to about 18 carbon atoms.

The molar ratio of acids to amines should be from about 1:1 to about 3:1. That is, if emulsion formation is to be avoided, the amount of acid should be at least sufiicient to neutralize the amine and preferably considerably more. The best acid-to-amine ratio ranges from about 1.5:1 to about 2.5:1, and is preferably about 2:1.

The concentration of the amine salt in the corrosioninhibiting composition may range from about 8 or 9 percent up to about 50 percent by weight. The lower concentrations, usually about 10 percent, are those which may be pre-formulated for squeezing into underground oil-bearing earth formations without further dilution Usually, however, a more concentrated form is sold because of easier handling and lower shipping costs. This more concentrated material is then diluted at the well before a squeeze job. Concentrations of more than 50 percent are not generally advisable because of higher viscosities, pour points, and emulsion-forming tendencies, unless a concentrate is deliberately prepared for shipping to a central location or into a remote area for dilution with local solvents. Such concentrates will be discussed later. In the usual inhibitor composition, the preferred concentration of amine salt is between about 20 and about 40 percent by weight, typically about 30 percent.

It has been found that alcohols, such as isooctanol, cooperate with amine salts to improve the corrosion-inhibiting ability of the amine salts. Thus, the addition of about percent of isooctanol to many amine salt corrosion-inhibiting compositions permits reducing the amine salt concentration from about 40 percent to about 30 percent with little loss in corrosion-inhibiting ability. In fact, in some cases, improved corrosion inhibition results. The action has been observed even in cases where there is little emulsion-forming tendency, so the function seems to be at least in part a cooperative action of the isooctanol with the film-forming amine salt. Thus, the isooctanol may be considered to be a cosurfactant which aids the ability of the amine salt to coat the metal surface to be protected.

In cases where emulsion formation is a problem, the presence of the alcohol and the lower concentration of amine salt tend to decrease the emulsion problem. As noted in my US. Pat. 2,756,211, a reduction in emulsion formation is generally accompanied by an improvement in corrosion inhibition.

Regardless of the explanation, the alcohol acts as an extender for the amine salt causing a lower concentration of amine salt to give the corrosion-inhibiting action of a higher concentration of amine salt. Thus, the alcohol can probably best be called an extender.

In the present composition, the emulsion-decreasing ability of a simple alcohol, such as isooctanol, is not as great as needed. Therefore, it has been necessary to employ another type of alcohols, the ethoxylated polypropylene glycols, which have much greater emulsion-preventing ability with the amine salts. These alcohols also have the cosurfactant and extender properties of isooctanol. See, for example, my Canadian Pat. 713,993. When sulfurized tall oil fatty acids are used, it has been found possible to avoid emulsions by use of a single type of ethoxylated polypropylene glycols rather than the combinations suggested in the Canadian patent. For use with sulfurized tall oil acids, the extenders should be based on polypropylene glycol having a molecular Weight from about 1,500 to about 2,500 and preferably about 2,000. The ethoxylated products should contain from about to about 20 percent by weight ethylene oxide and preferably about percent.

When the ethoxylated polypropylene glycols are used simply as demulsifiers, very low concentrations are usually employed. Thus, less than 1 percent of the materials may be effective as demulsifiers. When used as an extender, however, considerably higher concentration should be employed. This concentration should be at least about 2 percent by weight of the composition. An upper limit of about 8 or 10 percent is generally observed principally for economic reasons. A concentration of about 5 percent is usually preferred.

In Table I, it will be noted that a little water has been included in the preferred composition. This is to prevent haze formation upon long storage. Possibly the ethoxylated polypropylene glycol requires water of hydration which is supplied by the added water. This explanation may or may not be correct but a little water does avoid the hazing problem. The function of the inhibitor does not seem to be adversely affected by the haze, so that water is not really necessary. Therefore, the minimum permissible concentration of water is zero as shown in Table I. If too much water is added, the water in excess of that soluble in the composition tends to come out of solution and cause a haze. Therefore, the amount of water should not exceed 4 percent by weight.

Oil field chemicals to be used in northern areas usually require pour-point depressants to keep the compositions liquid at low temperatures. The present composition is no exception. As shown in Table I, the preferred composition includes about 10 percent by weight of a low-melting organic liquid, such as isopropanol. The preferred class of pour-point depressants includes the unsubstituted aliphatic alcohols containing from 1 to 4 carbon atoms per molecule. Other pour-point depressants, such as esters, ketones, ethers, and the like, can also be used if they have freezing points or pour points below about 30 F.

In warm areas, no pour-point depressant is required, so the minimum concentration is zero, as shown in Table I. In some applications, amine salts are used in alcohol solutions. An example is in light hydrocarbon streams, such as ethane, propane, and the like, where heavy hydrocarbons are undesirable. In such cases, the pour-point depressant and solvent may be the same, a low molecularweight alcohol. In such cases, the pour-point depressant concentration may be said to amount to as much as percent by weight of the composition.

Usually, the principal solvent for the amine salt is a hydrocarbon. Ordinarily, it is a petroleum fraction, such as kerosene, boiling somewhere between about F. and about 600 F., and preferably having a boiling range from about 300 to about 550 F. Petroleum fractions containing aromatics are the best solvents and are at least slightly preferred for this reason.

The concentration of solvent other than pour-point depressant is rarely below 40 percent in composition other than concentrates. The minimum concentration is usually at least about 50 percent and typically between about 50 percent and 60 percent by weight. The concentration may be as high as 90 percent in some cases, as explained above.

If a concentrate is to be prepared for dilution at a distant location, the preferred composition and possible ranges of concentration are presented in Table H.

In the concentrate, the amine salt may range from about 50 percent to about 90 percent by weight, preferably being about 75 percent. The other essential ingredient, the extender, may range from about 10 percent to about 30 percent by weight, preferably about 15 percent. No solvent at all may be used in a concentrate but use of about 10 percent is generally advisable to facilitate handling. Use of more than about 40 percent solvent brings the composition into the range of ordinary corrosion-inhibitor compositions, so the maximum concentration of solvent in a concentrate should be about 40 percent by weight.

Table III shows the results of tests run to determine the emulsifying tendencies of various amine salt compositions. All the inhibitor compositions were prepared according to the preferred formula of Table I. They differed only in the amount of sulfur, used to sulfurize the tall oil acids and the ratios of acid to amine used in preparing the salt. In all tests, the inhibitor composition was dissolved in a West Texas crude oil to form a percent by volume solution. Twenty-five milliliters of this solution and 25 milliliters of a brine containing 90 grams sodium chloride and 10 grams calcium chloride per liter were placed in a graduated cylinder. The mixture was shaken by hand for 50 strokes. It was then allowed to stand for 30 minutes, at which time the volumes of oil and water phases were noted.

In Test 1, the tall oil acids contained no sulfur. A comparison with Test 5, where no inhibitor at all was used, shows that this particular crude oil has only a minor emulsion problem ordinarily, but the presence of an amine salt of tall oil fatty acids causes some emulsion difliculties even in the presence of the ethoxylated polypropylene glycol.

Tests 2 and 4 show that by use of 2 or 3 moles of sulfur per mole of tall oil fatty acids, the emulsion problem can be completely overcome in the presence of the ethoxylated polypropylene glycol. Test 3 is simply a duplicate of Test 2 to be sure the results could be duplicated.

In Tests 1 through 4, twice as much acid was used as the amount necessary to neutralize the amine. In Tests 6 to 9, the mole ratio of acid to amine was 1:1. Test 6 shows that a stable emulsion formed when unsulfurized tall oil acids were used. Tests 7, 8 and 9 all used the same composition containing sulfurized tall oil. The variable results in the 3 tests show that while sulfurizing the tall oil in a neutral amine salt may help to some degree, the benefits are small and the results are erratic. It is apparent, therefore, that the amount of acid should be at least enough to neutralize the amine and preferably considerably more to provide the results shown in Tests 2, 3 and 4.

A water-dispersible form of inhibitor can be prepared by simply substituting about 1 percent of a dispersing agent for 1 percent of the solvent in the preferred formula of Table I. The dispersing agent is preferably ethoxylated lauryl alcohol containing about 23 moles of ethylene oxide per mole of lauryl alcohol. These compositions should be used with caution, however, since the dispersing agent tends to overcome, to at least some degree, the emulsionpreventing effects of the sulfurized tall oil and the ethoxylated polypropylene glycol.

Corrosion inhibition tests were run using compositions 2 and 4 of Table III. The tests were those usually employed for checking the inhibiting action of amine salts against corrosion by hydrogen sulfide, oxygen, carbon dioxide, and low molecular-weight organic acids. The excellent results obtained in all cases demonstrated that sulfurizing the tall oil acids and using their amine salts with ethoxylated polypropylene glycol as an extender did not adversely affect the corrosion-inhibiting properties. The results reported in Table III show that these changes did very favorably affect the emulsion-forming tendencies of the amine salts. Thus, it is apparent that I have accomplished the objects of my invention.

Many 'variations and alternates have been described above. Still others will occur to those skilled in the art. Therefore, I do not wish to be limited to the examples described, but only by the following claims.

I claim:

1. A corrosion-inhibiting composition consisting essentially of the following formulation:

fatty acid, said unsaturated fatty acid having from about 16 to about 22 carbon atoms per molecule and the moles of sulfur reacted with said acid being from about 1 to about 4 times the number of moles of said acid, the amine portion of said amine salt being selected from the group consisting of aliphatic amines and substituted imid'azolines, said amine having an aliphatic hydrocarbon radical containing from about 8 to about 22 carbon atoms.

the amount of said sulfurized unsaturated fatty acid being from about 1 to about 3 times the amount necessary to neutralize said amine,

said extender being an ethoxylated polypropylene glycol in which the polypropylene glycol has a molecular weight between about 1500 and about 2500 and the ethylene oxide being from about 10 to about 20 percent by weight of said ethoxylated polypropylene glycol,

said pour-point repressant being an unsubstituted alcohol containing from 1 to 4 carbon atoms per molecule,

and said solvent being selected from the group consisting of hydrocarbons boiling in the range from about F. to about 600 F. and alcohols having from 1 to 4 carbon atoms per molecule.

2. The composition of claim 1 in which said unsaturated fatty acid is the mixture of such acids obtained from tall oil, said amine is a diarnine having the formula RNl-I(CH NH where R is a mixture of hydrocarbon radicals containing from about 16 to about 18 carbon atoms per radical, and said solvent is a petroleum fraction boiling between about 300 F. and about 550 F.

3. The composition of claim 2 in which said sulfurized unsaturated fatty acid contains from about 2 to about 3 moles of sulfur per mole of unsaturated fatty acid, and the amount of said sulfurized unsaturated fatty acid is from about 1.5:1 to about 2.5:1 times the amount necessary to neutralize said amine.

5. A concentrate suitable for dilution with an organic solvent to form a liquid corrosion-inhibiting composition, said concentrate consisting essentially of the following formulation:

Material: Conc., percent by wt. Amine salt 50-90 Extender 10-30 Solvent 0-40 said amine salt being the salt of a sulfurized unsaturated fatty acid, said unsaturated fatty acid having from about 16 to about 22 carbon atoms per molecule and the moles of sulfur reacted with said acid being from about 1 to about 4 times the number of moles of said acid,

the amine portion of said amine salt being selected from the group consisting of aliphatic amines and substituted imidazolines, said amine having an aliphatic hydrocarbon radical containing from about 8 to about 22 carbon atoms,

the amount of said sulfurized unsaturated fatty acid being from about 1 to about 3 times the amount necessary to neutralize said amine,

said extender being an ethoxylated polypropylene glycol in Which the polypropylene glycol has a molecular weight between about 1500 and about 2500 and the ethylene oxide being from about 10 to about percent by weight of said ethoxylated polypropylene glycol,

and said solvent being selected from the group consisting of hydrocarbons boiling in the range from about 150 -F. to about 600 F. and alcohols having from 1 to 4 carbon atoms per molecule.

6. A concentrate suitable for dilution with an organic solvent to form a liquid corrosion-inhibiting composition, said concentrate consisting essentially of the following formulation:

Material: Conc., percent by wt. Amine salt F 50-90 Extender 10-30 Solvent 0-40 said salt being the salt of a sulfurized unsaturated fatty acid, said unsaturated fatty acid being the mixture of such acids obtained from tall oil,

the amine portion of said amine salt being a diamine having the formula RNH(CH NH where R is a mixture of hydrocarbon radicals containing from about 16 to about 18 carbon atoms per radical,

the amount of said sulfurized unsaturized fatty acid 8 being from about 1 to about 3 times the amount necessary mo neutralize said amine,

said extender being an ethoxylated polypropylene glycol in which the polypropylene glycol has a molecular weight between about 1500 and about 2500 and the ethylene oxide being from about 10 to about 20 percent by weight of said ethoxylated polypropylene y and said solvent being selected from the group consist ing of hydrocarbons boiling in the range from about F. to about 600" F. and alcohols having from '1 to 4 carbon atoms per molecule.

7. The composition of claim 6 in which said sulfurized unsaturated fatty acid contains from about 2 to about 3 moles of sulfur per mole of unsaturated fatty acid, and the amount of said sulfurized unsaturated fatty acid is from about 2 to about 3 times the amount necessary to neutralize said amine.

8. The composition of claim 7 in which the concentrations of ingredients are as follows:

LEON D. ROSDOL, Examiner I. GLUCK, Assistant Examiner US. Cl. X.R. 

